Recently, hybrid cars or electric vehicles are widely spread. A driving motor is mounted on such a vehicle, and a power source device for supplying power to the driving motor, is also mounted. lithium ion batteries, or nickel hydride batteries are generally used for the power source device for the vehicle.
By assembling a plurality of battery modules, this type of the power source device is often configured. In a case where a high output of the power source device is designed, a battery module including a plurality of battery cells connected in series, is used. In a case where a high capacity of the power source device is designed, a battery module including a plurality of battery cells connected in parallel, is used. In this way, the battery module is configured by connecting the plurality of the battery cells in the combination of series-connection or parallel-connection, according to a required performance of the power source device.
Since the battery cell is swollen and contracted corresponding to charge discharge or degradation, the battery module is formed by constraining and assembling the plurality of the battery cells. The battery source device having this type of the battery module is proposed in Patent Literature 1 as described in the following. A power source device includes a plurality of battery cells stacked in one direction, a pair of end plates respectively disposed on both ends, and constraining members coupled to the pair of the end plates. In the power source device of Patent Literature 1, the constraining members are respectively disposed at both side surfaces of the battery module, and coupled to the end plates. This configuration suppresses the swell of the battery cell through the constraining members and the end plates.
In the above-mentioned configuration, the constraining members press the battery cells through the end plates, and also its reaction force is applied to the constraining members. Concretely, a tensile force is applied to the constraining members in the stacked direction of the battery cells. Therefore, an experiment or the like in each of the battery module is carried out in advance, and then an external force (tensile force) which is applied to the constraining members due to the swells of the battery cells, is estimated. Then, in order not to break the constraining members against the estimated external force, a material, thickness, shape, or the like of the constraining member is designed.
In a case where the power source device is mounted on a vehicle, many types of the configurations can be adopted. Generally, assembling the vehicle and assembling the power source device are carried out in separate processes. Therefore, in a case where the power source device is mounted on the vehicle, the configuration where the battery module is fixed to a plate, outer case, or the like, is often adopted. For example, in a case of the power source device of Patent Literature 1, the battery module is mounted on the outer case, and the configuration where the end plates are fixed to the outer can be adopted. Concretely, through-holes for fixing are provided at the end plates, and the battery module is fixed to the outer case through fastening members such as bolts. According to this configuration, since the power source device is mounted on the vehicle by fixing the frame such as a plate, or an outer case to the vehicle body, the power source device in the assembled state can be easily fixed to the vehicle.